Process for the preparation of 2,3-pyridinedicarboximides

ABSTRACT

There is provided a process for the preparation of 2,3-pyridinedicarboximides having the structural formula I  
                 
 
     The 2,3-pyridinedicarboximides are useful as intermediates in the preparation of herbicidal 2-(2-imidazolin-2-yl)nicotinic acids, esters and salts.

BACKGROUND OF THE INVENTION

[0001] 2,3-Pyridinedicarboximides are useful as intermediates in thepreparation of herbicidal 2-(2-imidazolin-2-yl)nicotinic acids, estersand salts. Methods for the preparation of 2,3-pyridinedicarboximides areknown in the art (see, e.g., U.S. Pat. No. 4,748,244; U.S. Pat. No.4,754,033 and EP 308,084-A1). However, the methods described in thosepatents and patent application are not entirely satisfactory for thecommercial manufacture of 2,3-pyridinedicarboximides.

[0002] It is, therefore, an object of the present invention to providean effective and efficient process for the preparation of2,3-pyridinedicarboximides.

[0003] It is also an object of the present invention to provide acompound which is useful in the process of this invention.

[0004] These and other objects and features of the present inventionwill become more apparent from the detailed description thereof setforth below.

SUMMARY OF THE INVENTION

[0005] The present invention provides an effective and efficient processfor the preparation of a 2,3-pyridinedicarboximide having the structuralformula I

[0006] wherein

[0007] R is hydrogen, C₁-C₆alkyl or C₁-C₆alkoxymethyl;

[0008] R₁ is hydrogen, C₁-C₆alkyl, C(O)R₂,

[0009] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups,

[0010] benzyl optionally substituted on the phenyl ring with anycombination of from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitroor cyano groups, or

[0011] R₂ is C₁-C₆alkyl, benzyl or

[0012] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups;

[0013] R₃ and R₄ are each independently C₁-C₄alkyl; and

[0014] R₅ is cyano or CONH₂,

[0015] which process comprises reacting an oxime or hydrazone having thestructural formula II

[0016] wherein

[0017] R is as described above;

[0018] R₆ is C₁-C₆alkyl;

[0019] R₇ is OR₈ or NR₉R₁₀;

[0020] R₈ is hydrogen, C₁-C₆alkyl, C(O)R₁₁,

[0021] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups, or

[0022] benzyl optionally substituted on the phenyl ring with anycombination of from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitroor cyano groups;

[0023] R₁₁ is C₁-C₆alkyl, OR₁₂, NR₁₂R₁₃, benzyl or

[0024] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups;

[0025] R₁₂ and R₁₃ are each independently hydrogen, C₁-C₆alkyl, benzylor

[0026] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups; and

[0027] R₉ and R₁₀ are each independently hydrogen, C₁-C₆alkyl, benzyl or

[0028] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups,

[0029] with a maleimide having the structural formula III

[0030] wherein R₁ is as described above.

[0031] This invention also relates to the formula II oximes describedhereinabove.

DETAILED DESCRIPTION OF THE INVENTION

[0032] In one preferred embodiment of the present invention, an oxime orhydrazone represented by formula II is reacted with a maleimiderepresented by formula III, preferably in a temperature range of about20° C. to 160° C., in the presence of a solvent.

[0033] Advantageously, it has now been found that2,3-pyridinedicarboximides may be obtained in high yield and/or highpurity by the effective and efficient process of the present invention.

[0034] The 2,3-pyridinedicarboximides may be isolated by diluting thereaction mixture with water and filtering the formula I product from theaqueous mixture. The product formula I compounds may also be isolated byconcentrating the reaction mixture in vacuo and filtering the formula Iproduct from the concentrated mixture. Alternatively, the reactionmixture may be integrated into the process used to prepare the finalherbicidal agent without isolating the formula I compound.

[0035] Exemplary of halogen hereinabove are fluorine, chlorine, bromineand iodine.

[0036] In another embodiment of the present invention, a Lewis acid ispresent. Preferably, the Lewis acid is present in an amount up to aboutone molar equivalent relative to the formula II compound when R₈ ishydrogen. Lewis acids suitable for use in the present invention includeany conventional Lewis acids. Preferred Lewis acids include aluminumchloride and titanium(IV) chloride.

[0037] Solvents suitable for use in the process of the present inventionpreferably have a boiling point of at least about 60° C. and includearomatic hydrocarbons such as toluene, xylenes, mesitylene and mixturesthereof; halogenated aromatic hydrocarbons such as mono- anddihalobenzenes and mixtures thereof; polynuclear aromatic hydrocarbonssuch as naphthalene, alkylnaphthalenes and mixtures thereof; ethers suchas tetrahydrofuran and mixtures thereof; glycols such as1,2-diethoxyethane and mixtures thereof; an alkanoic acid such as aceticacid, propionic acid and mixtures thereof; an alkanoic acid/watermixture such as an acetic acid/water mixture; acetonitrile; anacetonitrile/water mixture; and mixtures thereof. Preferred solventsinclude toluene, xylenes, mesitylene, acetonitrile, anacetonitrile/water mixture, acetic acid and mixtures thereof withtoluene and acetonitrile being more preferred.

[0038] In another preferred embodiment of the present invention, oximesof formula II wherein R₇ is OR₈ are reacted with maleimides of formulaIII preferably at a temperature range of about 60° C. to 160° C., morepreferably about 75° C. to 135° C. And hydrazones of formula II whereinR₇ is NR₉R₁₀ are reacted with maleimides of formula III preferably at atemperature range of about 20° C. to 160° C., more preferably about 20°C. to 135° C.

[0039] In a further preferred embodiment of the present invention, abase is present when R is C₁-C₆alkoxymethyl. The base is used to reducethe amount of 5-methyl-2,3-pyridinedicarboximides which are produced asundesirable by-products when R is C₁-C₆alkoxymethyl.

[0040] Bases suitable for use in the present invention include, but arenot limited to, tri(C₂-C₄alkyl)amines such as triethylamine,N,N-diethylisopropylamine, N,N-diisopropylethylamine and the like,alkali metal acetates such as sodium acetate, potassium acetate and thelike, and mixtures thereof. Preferred bases include triethylamine,sodium acetate and potassium acetate. The base is preferably present inan amount of at least about one molar equivalent relative to the formulaII compound.

[0041] In a further embodiment of the present invention, a phasetransfer catalyst is present when the base is present. Preferably, thephase transfer catalyst is present when the alkali metal acetate ispresent. Phase transfer catalysts suitable for use in the presentinvention include any conventional phase transfer catalysts. Preferredphase transfer catalysts include crown ethers such as 18-crown-6 and15-crown-5.

[0042] In a preferred process of the present invention,

[0043] R is hydrogen, C₁-C₄alkyl or C₁-C₄alkoxymethyl;

[0044] R₁ is hydrogen, C₁-C₄alkyl,

[0045] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups, or

[0046] R₃ and R₄ are each independently C₁-C₄alkyl;

[0047] R₅ is cyano or CONH₂;

[0048] R₆ is C₁-C₄alkyl;

[0049] R₇ is OR₈; and

[0050] R₈ is hydrogen or C₁-C₆alkyl.

[0051] In a more preferred process of the present invention,

[0052] R is hydrogen, methyl, ethyl or methoxymethyl;

[0053] R₁ is methyl, phenyl or

[0054] R₅ is cyano or CONH₂;

[0055] R₆ is methyl or ethyl;

[0056] R₇ is OR₈; and

[0057] R₈ is hydrogen or methyl.

[0058] Formula II oximes wherein

[0059] R₇ is OR₈; and

[0060] R₈ is hydrogen, C₁-C₆alkyl,

[0061] phenyl optionally substituted with any combination of from one tofour halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups, or

[0062] benzyl optionally substituted on the phenyl ring with anycombination of from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitroor cyano groups,

[0063] may be prepared by reacting a 3-alkoxy-2-propenal of formula IVwith a substituted hydroxylamine of formula V optionally in the presenceof a base. The reaction scheme is shown below in Flow Diagram I.

[0064] Alternatively, oximes of formula II wherein R₈ is C₁-C₆alkyl maybe prepared by reacting a formula II compound wherein R₈ is hydrogenwith a dialkyl sulfate of formula VI in the presence of a base such assodium hydroxide or an alkali metal alkoxide. The reaction scheme isshown in Flow Diagram II.

[0065] Formula II oximes wherein R₈ is C(O)R₁₁ may be prepared byreacting a formula II compound wherein R₈ is hydrogen with an acidchloride of formula VII or an anhydride of formula VIII as shown in FlowDiagram III.

[0066] Formula II hydrazones may be prepared by reacting a3-alkoxy-2-propenal of formula IV with a hydrazine of formula IXoptionally in the presence of an acid catalyst such as acetic acid. Thereaction scheme is shown in Flow Diagram IV.

[0067] 3-Alkoxy-2-propenal compounds of formula IV may be preparedaccording to the procedures described by E. Breitmaier, et al inSynthesis, pages 1-9 (1987). Maleimide compounds of formula III areknown in the art and may be prepared according to the proceduresdescribed by M. Cava, et al in Organic Synthesis, 41, page 93 (1961).

[0068] Alternatively, formula IV compounds wherein R is methoxymethylmay be prepared by reacting a 3-(dialkylamino)-2-propenal of formula Xwith formaldehyde and methanol in the presence of a mineral acid such assulfuric acid to form a 3-(dialkylamino)-2-(methoxymethyl)-2-propenal offormula XI, and reacting the formula XI compound with a base such as analkali metal hydroxide and a dialkyl sulfate of formula VI. The reactionscheme is shown in Flow Diagram V.

[0069] The present invention also provides a process for the preparationof a herbicidal 5-(alkoxymethyl)-2-(2-imidazolin-2-yl)-nicotinic acid,ester and salt compound having the formula

[0070] wherein

[0071] R is as defined above;

[0072] R₁₄ is C₁-C₄ alkyl;

[0073] R₁₅ is C₁-C₄ alkyl, C₁-C₆ cycloalkyl or R₁₄ and R₁ when takentogether with the atom to which they are attached, represent a C₃-C₆cycloalkyl group optionally substituted with methyl and

[0074] R₁₆ is hydrogen, diloweralkylimino,

[0075] C₁-C₁₂ alkyl optionally substituted with one of the followinggroups: C₁-C₃ alkoxy, halogen, hydroxy, C₃-C₆ cycloalkyl, benzyloxy,furyl, phenyl, halophenyl, lower alkylphenyl, lower alkoxyphenyl,nitrophenyl, carboxyl, loweralkoxycarbonyl, cyano ortriloweralkylammonium;

[0076] C₃-C₁₂ alkenyl optionally substituted with one of the followinggroups: C₁-C₃ alkoxy, phenyl, halogen or loweralkoxycarbonyl or with twoC₁-C₃ alkoxy groups or two halogen groups;

[0077] C₃-C₆ cycloalkyl optionally substituted with one or two C₁-C₃alkyl groups; or

[0078] a cation preferably selected from the group consisting of alkalimetals, alkaline earth metals, manganese, copper, iron, zinc, cobalt,lead, silver, nickel, ammonium and organic ammonium;

[0079] which process comprises:

[0080] (a) preparing a compound having the formula I

[0081] wherein R and R₁ are as defined above by a process as definedabove; and

[0082] (b) converting the compound having formula I into the compoundhaving the formula XII.

[0083] The term “lower” as used above in relation to alkyl and alkoxygroups means that the alkyl or alkoxy group contains 1 to 6, preferably1 to 4, carbon atoms.

[0084] The conversion of the compound having formula I into the compoundhaving formula XII may be carried out in a variety of ways. One may planroutes by combining reactions known for the conversion of one carboxylicacid derivative into another.

[0085] Methods that may be used to create the imidazolinone herbicidesare illustrated in the book “The Imidazolinone Herbicides” edited by D.L. Shaner and S. L. O'Connor, published 1991 by CRC Press, Boca Raton,Florida with particular reference to Chapter 2 entitled “Synthesis ofthe Imidazolinone Herbicides”, pages 8-14 and the references citedtherein. The following patent literature references also illustrate themethods that may be used to convert the carboxylic acid derivatives intoimidazolinone final products:

[0086] U.S. Pat. Nos. 5,371,229; 5,334,576; 5,250,694; 5,276,157;5,110,930; 5,122,608; 5,206,368; 4,925,944; 4,921,961; 4,959,476;5,103,009; 4,816,588; 4,748,244; 4,754,033; 4,757,146; 4,798,619;4,766,218; 5,001,254; 5,021,078; 4,723,011; 4,709,036; 4,658,030;4,608,079; 4,719,303; 4,562,257; 4,518,780; 4,474,962; 4,623,726;4,750,978; 4,638,068; 4,439,607; 4,459,408; 4,459,409; 4,460,776;4,125,727 and 4,758,667, and European Patent Application Nos.EP-A-0-041,623 and EP-A-0-308,084.

[0087] In order to facilitate a further understanding of the invention,the following examples are presented primarily for the purpose ofillustrating more specific details thereof. The invention should not bedeemed limited by the examples as the full scope of the invention isdefined in the claims.

EXAMPLE 1

[0088] Preparation of the Oxime of 3-ethoxy-2-methyl-2-propen-1-one,(E)- and (Z)-

[0089] 3-Ethoxy-2-methyl-2-propenal, (E)- and (Z)- (30.0 g, 0.25 mol) isadded dropwise to a mixture of hydroxylamine sulfate (33.0 g, 0.2 mol)and sodium acetate (33.4 g, 0.4 mol) in water (200 g). The resultantreaction mixture is stirred overnight and filtered to obtain a solid.The solid is washed with water and dried to give the title product as awhite solid (23.2 g, mp 78° C., 71% yield) Using essentially the sameprocedure, but substituting methoxylamine hydrochloride for hydroxyl-amine sulfate, the O-methyloxime of 3-ethoxy-2-methyl-2-propen-1-one,(E)- and (Z)- is obtained as a yellow oil.

EXAMPLE 2

[0090] Preparation of the O-methyloxime of3-ethoxy-2-methyl-2-propen-1-one, (E)- and (Z)-

[0091] A mixture of the oxime of 3-ethoxy-2-methyl-2-propen-1-one, (E)-and (z)- (0.5 g, 3.87 mmol) and potassium tert-butoxide (0.48 g, 4.2mmol) in tetrahydrofuran is stirred for ten minutes at 10° C., treateddropwise with dimethyl sulfate (0.59 g, 4.6 mmol), stirred for two hoursand filtered. The resultant filtrate is concentrated in vacuo to givethe title product as a yellow oil (0.74 g, 100% yield).

EXAMPLE 3

[0092] Preparation of 5-Methyl-N-phenyl-2,3-pyridine-dicarboximide

[0093] A solution of N-phenylmaleimide (1.69 g, 9.8 mmol) in toluene (16g) is refluxed for 24 hours. During the reflux period, the O-methyloximeof 3-ethoxy-2-methyl-2-propen-1-one, (E)- and (Z)- (1.57 g, 11 mmol) isadded portionwise to the reaction mixture. The final reaction 10 mixtureis then concentrated in vacuo to give the title product as a orangesolid (1.2 g, 52% yield).

EXAMPLES 4-7

[0094] Using essentially the same procedure as described in Example 3,but substituting the oxime of 3-ethoxy-2-methyl-2-propen-1-one, (E)- and(Z)- for the O-methyl-oxime of 3-ethoxy-2-methyl-2-propen-1-one, (E)-and (Z)-, 5-methyl-N-phenyl-2,3-pyridinedicarboximide is produced in theyields shown in Table I. TABLE I Preparation of5-Methyl-N-phenyl-2,3-pyridinedicarboximide Exam- Equivalents of N-Lewis Acid/ Hours % ple phenylmaleimide Equivalents Solvent RefluxedYield 4 0.3 AlCl₃/0.2 Toluene 27 20 5 0.3 TiCl₄/0.3 Toluene 10 10 6 0.2— H₂O/ 12 15 CH₃CN (1:1) 7 2.0 — CH₃CO₂H  9 15

EXAMPLE 8

[0095] Preparation of 3-(Dimethylamino)-2-(methoxymethyl)-2-propenal,(E)- and (Z)-

[0096] Concentrated sulfuric acid (1 mL) is slowly added to a solutionof 3-(dimethylamino)-2-propenal (200 g, 2.01 mol) and paraformaldehyde(90 g, 3 mol) in methanol (1 L). The resultant solution is ref luxedovernight, concentrated in vacuo to a volume of 200 mL, diluted withtoluene and distilled until the vapor temperature is 105° C. Thesolution is then concentrated in vacuo to give the title product as anorange oil (251.4 g, 87% yield).

EXAMPLE 9

[0097] Preparation of 3-Methoxy-2-(methoxymethyl)-2-propenal, (E)- and(Z)-

[0098] A solution of 3-(dimethylamino)-2-(methoxymethyl)-2-propenal,(E)- and (Z)- (53.06 g, 0.37 mol) and sodium hydroxide solution (29.7 g,50%, 0.37 mol) in methanol (60 mL) is refluxed for 20 minutes andconcentrated in vacuo to obtain a white solid. A solution of the solidin water (250 mL) is treated dropwise with dimethyl sulfate (46.75 g,0.37 mol), stirred at room temperature for one hour and extracted withmethylene chloride. The organic extract is dried over anhydrous sodiumsulfate, concentrated in vacuo and distilled to give the title productas a colorless liquid (19.66 g, bp 80° C./0.5 mm Hg, 41% yield).

EXAMPLE 10

[0099] Preparation of5-(Methoxymethyl)-N-phenyl-2,3-pyridinedicarboximide

[0100] A solution of methoxyamine hydrochloride (1.7 g, 20 mmol) andsodium acetate (2.1 g, 25.6 mmol) in water (30 mL) is treated dropwisewith 3-methoxy-2-(methoxymethyl)-2-propenal, (E)- and (Z)- (2.2 g, 16.9mmol), stirred at room temperature for 30 minutes and extracted withmethylene chloride. The organic extract is dried over anhydrous sodiumsulfate and concentrated in vacuo to obtain the O-methyloxime of3-methoxy-2-(methoxymethyl)-2-propen-1-one. A mixture of the resultantO-methyloxime of 3-methoxy-2-(methoxymethyl)-2-propen-1-one,N-phenylmaleimide (2.9 g, 16.8 mmol) and diisopropylethylamine (2.2 g,17.0 mmol) in toluene (50 mL) is refluxed for 23 hours. During thereflux period, additional N-phenylmaleimide (2.9 g, 16.8 mmol) is addedto the reaction mixture. The final reaction mixture is concentrated invacuo to give the title product as a solid (0.36 g, 8% yield) having a5-(methoxymethyl)-N-phenyl-2,3-pyridinedicarboximide to5-methyl-N-phenyl-2,3-pyridinedicarboximide ratio of 50:1.

EXAMPLE 11

[0101] Preparation of 3-Ethoxy-2-methylacrolein Dimethylhydrazone, (E)-and (Z)-

[0102] A mixture of 3-ethoxy-2-methyl-2-propenal, (E)- and (Z)- (4.0 g,35 mmol), 1,1-dimethylhydrazine (2.73 g, 46 mmol) and acetic acid (0.04g, 0.7 mmol) in diethyl ether is refluxed for one hour, cooled, washedsequentially with water and brine, dried over anhydrous magnesiumsulfate, and concentrated in vacuo to give the title product as a yellowoil.

EXAMPLE 12

[0103] Preparation of 5-Methyl-N-phenyl-2,3-pyridine-dicarboximide fromN-phenylmaleimide and 3-ethoxy-2-methylacrolein Dimethylhydrazone, (E)-and (Z)-

[0104] A solution of N-phenylmaleimide (1.1 g, 6.4 mmol) in acetonitrileis refluxed for 19 hours. During the reflux period,3-ethoxy-2-methylacrolein dimethylhydrazone, (E)- and (Z)- (1.2 g, 7.6mmol) is added portionwise to the reaction mixture. The final reactionmixture is then concentrated in vacuo to give the title product as adark oil (0.23 g, 15% yield).

We claim:
 1. A process for the preparation of a2,3-pyridinedicarboximide having the structural formula I

wherein R is hydrogen, C₁-C₆alkyl or C₁-C₆alkoxymethyl; R₁ is hydrogen,C₁-C₆alkyl, C(O)R₂, phenyl optionally substituted with any combinationof from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyanogroups, benzyl optionally substituted on the phenyl ring with anycombination of from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitroor cyano groups, or

R₂ is C₁-C₆alkyl, benzyl or phenyl optionally substituted with anycombination of from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitroor cyano groups; R₃ and R₄ are each independently C₁-C₄alkyl; and R₅ iscyano or CONH₂, which process comprises reacting an oxime or hydrazonehaving the structural formula II

wherein R is as described above; R₆ is C₁-C₆alkyl; R₇ is OR₈ or NR₉R₁₀;R₈ is hydrogen, C₁-C₆alkyl, C(O)R₁₁, phenyl optionally substituted withany combination of from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy,nitro or cyano groups, or benzyl optionally substituted on the phenylring with any combination of from one to four halogen, C₁-C₄alkyl,C₁-C₄alkoxy, nitro or cyano groups; R₁₁ is C₁-C₆alkyl, OR₁₂, NR₁₂R₁₃,benzyl or phenyl optionally substituted with any combination of from oneto four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups; R₁₂ andR₁₃ are each independently hydrogen, C₁-C₆alkyl, benzyl or phenyloptionally substituted with any combination of from one to four halogen,C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups; and R₉ and R₁₀ are eachindependently hydrogen, C₁-C₆alkyl, benzyl or phenyl optionallysubstituted with any combination of from one to four halogen,C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups, with a maleimide havingthe structural formula III

wherein R₁ is as described above.
 2. The process according to claim 1wherein R is hydrogen, C₁-C₄alkyl or C₁-C₄alkoxymethyl; R₁ is hydrogen,C₁-C₄alkyl, phenyl optionally substituted with any combination of fromone to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups, or

R₆ is C₁-C₄alkyl; R₇ is OR₈; and R₈ is hydrogen or C₁-C₆alkyl.
 3. Theprocess according to claim 2 wherein R is hydrogen, methyl, ethyl ormethoxymethyl; R₁ is methyl, phenyl or

R₆ is methyl or ethyl; and R₈ is hydrogen or methyl.
 4. The processaccording to claim 1 wherein the formula II oxime or hydrazone isreacted with the formula III maleimide in the presence of a solvent. 5.The process according to claim 2 wherein the solvent is selected fromthe group consisting of an aromatic hydrocarbon, a halogenated aromatichydrocarbon, a polynuclear aromatic hydrocarbon, a glycol, an alkanoicacid, an alkanoic acid/water mixture, acetonitrile, anacetonitrile/water mixture, and mixtures thereof, and the boiling pointof the solvent is at least about 60° C.
 6. The process according toclaim 5 wherein the solvent is selected from the group consisting oftoluene, a xylene, mesitylene, acetonitrile, an acetonitrile/watermixture, acetic acid and mixtures thereof.
 7. The process according toclaim 6 wherein the solvent is toluene or acetonitrile.
 8. The processaccording to claim 1 wherein the formula II oxime is reacted with theformula III maleimide at a temperature of about 60° C. to 160° C.
 9. Theprocess according to claim 8 wherein the temperature is about 75° C. to135° C.
 10. The process according to claim 1 wherein the formula IIhydrazone is reacted with the formula III maleimide at a temperature ofabout 20° C. to 160° C.
 11. The process according to claim 10 whereinthe temperature is about 20° C. to 135° C.
 12. The process according toclaim 1 further comprising a Lewis acid.
 13. The process according toclaim 12 wherein the Lewis acid is aluminum chloride or titanium(IV)chloride.
 14. The process according to claim 1 further comprising a basewhen R is C₁-C₆alkoxymethyl.
 15. The process according to claim 14wherein the base is selected from the group consisting of atri(C₂-C₄alkyl)amine, an alkali metal acetate and mixtures thereof. 16.A compound having the structural formula

wherein R is hydrogen, C₁-C₆alkyl or C₁-C₆alkoxymethyl; R₆ isC₁-C₄alkyl; R₈ is hydrogen, C₁-C₆alkyl, C(O)R₁₁. phenyl optionallysubstituted with any combination of from one to four halogen,C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyano groups, or benzyl optionallysubstituted on the phenyl ring with any combination of from one to fourhalogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or -cyano groups; R₁₁ isC₁-C₆alkyl, OR₁₂, NR₁₂R₁₃, benzyl or phenyl optionally substituted withany combination of from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy,nitro or cyano groups; and R₁₂ and R₁₃ are each independently hydrogen,C₁-C₆alkyl, benzyl or phenyl optionally substituted with any combinationof from one to four halogen, C₁-C₄alkyl, C₁-C₄alkoxy, nitro or cyanogroups, and the cis and trans isomers thereof.
 17. The compoundaccording to claim 16 wherein R is hydrogen, C₁-C₄alkyl orC₁-C₄alkoxymethyl; R₆ is C₁-C₄alkyl; and R₈ is hydrogen or C₁-C₆alkyl.18. The compound according to claim 17 wherein R is hydrogen, methyl,ethyl or methoxymethyl; R₆ is methyl or ethyl; and R₈ is hydrogen ormethyl.
 19. The compound according to claim 18 selected from the groupconsisting of the O-methyloxime of 3-ethoxy-2-methyl-2-propen-1-one; theO-methyloxime of ³-methoxy-2-(methoxymethyl)-2-propen-1-one; the oximeof 3-ethoxy-2-methyl-2-propen-1-one; and the oxime of3-methoxy-2-(methoxymethyl)-2-propen-1-one.
 20. A process for thepreparation of a herbicidal imidazolinone compound having the formulaXII

wherein R is as defined in claim 1; R₁₄ is C₁-C₄ alkyl; R₁₅ is C₁-C₄alkyl, C₃-C₆ cycloalkyl or R₁₄ and R₁₅ when taken together with the atomto which they are attached, represent a C₃-C₆ cycloalkyl groupoptionally substituted with methyl and R₁₆ is hydrogen,diloweralkylimino, C₁-C₁₂ alkyl optionally substituted with one of thefollowing groups: C₁-C₃ alkoxy, halogen, hydroxy, C₃-C₆ cycloalkyl,benzyloxy, furyl, phenyl, halophenyl, lower alkylphenyl, loweralkoxyphenyl, nitrophenyl, carboxyl, loweralkoxycarbonyl, cyano ortriloweralkylammonium; C₃-C₁₂ alkenyl optionally substituted with one ofthe following groups: C₁-C₃ alkoxy, phenyl, halogen orloweralkoxycarbonyl or with two C₁-C₃ alkoxy groups or two halogengroups; C₃-C₆ cycloalkyl optionally substituted with one or two C₁-C₃alkyl groups; or a cation which process comprises: (a) preparing acompound having the formula I

wherein R and R₁ are as defined in claim 1 by a process as claimed inclaim 1; and (b) converting the compound having formula I into thecompound having the formula XII.